This invention relates, in general, to voltage regulators and regulator buffers in integrated circuitry technology and, in particular, to voltage regulators and regulators buffers for CML devices.
Voltage regulators have been developed to supply a constant output voltage for logic circuits within a limited range of variations in the supply voltage. One prior art regulator circuit utilizes a resistor between the power supply voltage and the base of a shunt transitor to compensate for variations in the supply of voltage. Since such a resistor is also subject to supply voltage variations, it does not completely eliminate the first order effect of the voltage variations on the shunt transistor. Consequently, the output voltage of the regulator is not constant. This prior art circuit is shown in the U.S. Pat. to Allen, et al, No. 3,970,876.
Another prior art regulator circuit uses a supply feedback amplifier coupled to the shunt transistor of the voltage regulator. The resistances of the supply feedback amplifier are carefully matched to the resistances in the regulator so that a fluctuation in supply voltage is sensed by the supply feedback section to maintain current through the shunt transistor constant thus providing a regulated voltage output. This circuit is shown in the application for U.S. patent by R. K. Tam, Ser. No. 745,660, filed Nov. 29, 1976, now U.S. Pat. No. 4,100,477. However, this circuit also required an additional feedback from an unbalancing circuit to the output node.
Another approach in the prior art is to eliminate the effect of the shunt transistor from the regulator entirely by utilizing pairs of transistors with matched current densities and high current gains to supply a constant output voltage. This circuit is shown in the application for U.S. patent, Ser. No. 772,767 by R. K. Tam, filed Feb. 28, 1977, now U.S. Pat. No. 4,100,478.
Finally, it should be pointed out that while the prior art Stopper regulator was invented for power supplies at 2.7.+-.30% and the two Tam regulators were invented for voltages of 4.8 V.+-.25%, still a need exists for a regulator and regulator buffer which will operate better at 2.7 V.+-.30% ie. over a range of 3.5 V to 1.9 V without being affected by such voltage fluctuations as mentioned above.
Accordingly it is a primary object of this invention to provide a regulator which is fully compensated for supply voltage variation by eliminating such effects on the current flow through a main or output transistor.
A further object of this invention is to provide a regulator with shunt circuitry which includes circuit means for tracking any variation in supply voltage and causing one transistor coupled in parallel with an output transistor to shunt current from the flow path through the output transistor thus providing a constant voltage output from the regulator.
Still another object of this invention is to provide a regulator buffer connected to the output of this same regulator and to the same supply voltage for providing a constant voltage output for series gated CML devices.
Still another and more specific object of this invention is to provide a regulator and regulator buffer operable with a power supply voltage of 2.7 V.+-.30%.